1. Field
The present invention relates to a method and apparatus for expanding a dynamic range of a display device so as to implement High Dynamic Range (HDR) using a RGBW-type pixel array.
2. Related Art
An active matrix-type Liquid Crystal Display (LCD) device is a switching device that displays an image using a Thin Film Transistor (TFT). The LCD device includes a display panel and a Back Light Unit that irradiates light on the display panel.
There are increasing demands for an HDR display device which displays a reproduced image to make a user to feel as if he is seeing a real scene. The HDR display device needs to secure a physical capability of expressing irradiation at thousands of nits and a technology of converting Low Dynamic Range (LDR) contents to be suitable for the HDR display device. Many efforts have been made to study the HDR display device, but there is no relevant technology that is widely used.
For example, attempts have been made to implement a High Dynamic Range (HDR) display device based on a LCD device, but to no avail. One of the attempts is U.S. Patent Publication No. 2011/0279749 A1 (Nov. 17, 2011) which seeks a high dynamic range by laminating two LCD panel on a backlight unit, wherein the one LCD panel is used to display an image and the other LCD panel is used as a dimming panel for controlling brightness in a local area. However, this art uses two LCD panels so it is thick and requires more costs. In addition, it enhances contrast by making a dark image even darker, not making a bright image much brighter, so that it cannot implement a HDR display device in the true sense of the term.
Improving contrast simply by using a local dimming method may lead to a linear increase in brightness properties, possibly causing brightness of an intermediate gray scale to increase. As a result, if contrast is enhanced using only the local dimming method, an observer may feel an image glaring.